Electric circuit breaker



March 21, 1933. w PAUL 1,902,464

ELECTRIC C IRCUIT BREAKER Filed July 28, 1931 Inventor: William E. Paul,

His Abtor'neg.

Patented Mar. 21, 1933 UNITED STATES- PATENT OFFICE WILLIAM E; PAUL, OF SCHENECTAD Y, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK ELEO'IRIC CIRCUIT BREAKER Application filed July 28, 1931.

- v My invention relates to electric circuit breakers, more particularly to switches of the fluid-blast type wherein arcing within a pressure confining chamber is utilized to P cause a blast of insulating liquid from sald chamber interrupting the circuit A principal object of my invention 15 the provision of an improved circuit breaker of the aforesaid type which shall clear the circuit by a comparatively limited separation of the switch contacts, and avoid excessive arcing pressures within the pressure confining chamber.

My invention will be more fully set forth in the following description referring to the accompanying drawing, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this v specification.

The single figure of the drawing is an elevational view, partly in section, of an electric circuit breaker embodying my invention.

The circuit breaker shown by way of example is of the type disclosed and claimed in my copending application Serial No. 519,757, filed March 3, 1931, for electric circuit break ers, and comprises a tank 1 containing an insulating liquid 2, as oil, in which is immersed a casing 3 forming a pressure confining chamber 4. C'oacting circuit controlling contacts including a movable bridging member 5 and stationary contact structures 6 and 7 of the well known finger type are disposed with- 5 in the pressure confining chamber 4, the contacts forming two breaks in series upon downward or circuit opening movement of the bridging member 5. The stationary contact structure 7 is positioned above and-adjacent a pressure relief opening 8 in the casing 3 arranged so that the main are drawnopposite the relief opening. The other arc formed between the stationary contact struc- 5 ture 6 and the bridging member 5 is more remotely positioned with respect to the relief opening and generates pressure causing a blast of insulating liquid from the chamber.

4 through the relief opening 8 and across the 9 main arc;

keted as at Serial No. 553,603.

As illustrated, the oil switch tank 1 completely fills the chamber 4, the oil levelbeing preferably above the top of the chamber so as to avoid an air cushion or pocket therein,-the upper part of the chamber 4 being suitably vented for permitting escape of gas from the top of the (chamber and refilling of the same with oil after a circuit interrupting operation.

Referring more particularly to the contact structure and operating means therefor, the bridging member 5, which is of the conventional wedge t pe, is suitably connected to a lift rod 9 likewise connected to a transverse insulating member 10 for operating a number of similar polyphase units. In the upper or closed circuit position shown the bridging member-is in engagement with the contact structures 6 and 7, the opposing contact fingers of which are resiliently mounted with respect to the conducting supporting blocks 11 and 12 carried by the lower ends of the andbiased apart 13 and 14 extend the conductor studs 13 and 14 respectively, suitable terminal structure being provided at the upper ends thereof.

The insulating bushings 13 and 14 extend through and are carried by the cover 1 of the switch tank, the cover being suitably gasand clamped, as by the retain,- ing bolts 16, to the casing 1 thereby insuring a strong and fluid-tight switch casing. Suitably mounted on the cover member 1 is the operating linka e mechanism 17 which may be of any suitable design for effecting vertical reciprocal movement of the lift rod 9. In the present instance, ly mounted at 19 on an the cover member '1' is actuated by toggle 20 through a crank 21 and operating link 22'. The lever 18 is operatively connected at one end to the lift rod 9, as by a roller 18 carried by the lever 18 and extending between abutments on the rod 9. The operating link 22 is connected to any sui able motive means as a solenoid, motor or manually operated mechanism. The lever 18 is normally biased a lever 18 piv0talexterior portion of,

clockwise towards open circuit position by a compression spring 23 connected as at 24' to the cover 1 and hearing at its free end on a member 25 connected to the lever 18, the spring being guided by a rod 26 slidable within the member 25.

Since the pressures generated within the chamber 4 may be quite large, the casing 3 is preferably of steel, as is thetank 1, the bottom wall of the casing 3 being welded or otherwise suitably secured at three sides to the side walls of the tank 1 so that the tank actually forms three side walls of the pressure chamber. The front wall of the pressure chamber is formed by a steel plate welded to the opposite walls of the tank 1. The chamber is provided with an insulating lining 27 along its side andbottom walls, the' ,lining at the front or pressure relief side having an opening somewhat smaller than and substantially in registry with the prestors and stationary contact structure while at the same time preventing formation of a gas or air cushion in the upper part of the chamber in the event that the oil level within the tank drops asmall amount Formation. of a gas pocket or cushion in the upper part of the chamber is undesirable since a substantially incompressible liquid should fill the chamber for producing the oil. blast. hereinafter described. With this arrangement, adequate ereepage distance is provided between the contacts and the plate 29, which maintains the insulating structure in position against high pressures, and the creepage space is substantially filledwith solid insulation. The tank 1 is moreover protected against bursting forces by a channel member 30 which encircles and'i's welded to'the outer wall of the tank.

When the bridging member 5 is lowered in )response to tripping of the switch to cause separation of the contacts, the main currentcarrying fingersfi" and 7' are first disengaged, the current being progressively transferred tothe longer contact fingers until the final separation takes place at the extreme outer fingers'comprising the arcing contact fingers. Immediately upon formation of the pressure generating are, the pressure created within the chamber 4 forces a blast-of oil at high velocity through the relief opening 8.

For the purpose of avoiding excessive pressures within the chamber 4, the contact strucin the ture at the pressure generating break is provided with means maintaining substantially constant the length of the arc during circuit interruption which is effected in the initial circuit opening movement, As is well known, the pressure generated by an are drawn in an insulating liquid, as oil, depends not only upon the duration and intensity of the are but also upon its length. For example, a short are maintained for a complete cycle of alternating current may generate less pressure than a longer are within one-half cycle. Since adequate pressure for the purpose required may be generated by a comparatively short are, the advantage in maintaining the pressure generating are at a substantially minimum length up to the point of circuit interruption is at once apparent. To this end the stationary contact structure 6 is provided with an arcing member 31 which is electrically connected to the supporting block 11 and extendsdownwardly in a direction parallel with the movement of the bridging member 5. As illustrated, the adjacent outer end of the-bridging member 5 is spaced a short distance from the arcing member 31 so that when the bridging member separates from the arcing fingers, the arc is at once transferred to the member 31 by reason of the magnetic blowout action inherent in a loop circuit. Accordingly, during the initial separation of the contacts the length of are between the bridging member 5 and arcing member 31 will remain constant, the arc lengthening only when the bridging member passes below-the level of the lower outturned end of the arcing member. During this time a short arc is likewise formed between the contact structure 7 and the bridging member opposite the relief opening '8; Since the are so formed is wholly within the path of the blast of insulating liquid through the relief opening the interrupting action will be very effective and normally is. completed before lengthening of the. arc gap at the pressure generating break.

In case of heavy short-circuit currents, interruptionby a continued strong blast of insulating liquid through a comparatively short arc is more effective than in the case where the arc is partly within and outside of the blast. For the purpose of effecting a strong blast of insulating liquid through a predetermined short length of arc there is provided means retarding the separation of the contacts at a definite point so that the arc is entirely within the blast and is not appreciably increased in length during the circuit interruption. In the present instance the retarding means comprises a dashpot arrangement operatively connected to the bridging member 5 comprising a plunger 32 secured to the transverse member 10 and guided by the insulating structure 33 through the opening 32 ottom wall of the pressure chamber.

The dashpot casing comprises a cylindrical member 34 immersed in the oilbeneath the chamber 4 having fluid vents 35 exteriorly of the chamber 4 and restricted vents 36 at the I bottom of the tank 1., The cylinder 34 which is suitably positioned between the bottom of the tank 1 and the casing 3 is in alignment with the opening 32 and receives the plunger 32 when the bridging member is in its lowermost open circuit position. The size of the Vents 35 is so designed that comparatively little resistance is offered the plunger 32 during the first part of the opening movement, that is until the plunger 32 begins to cover the Vents 35. At that point, there is a decided dashpot or retarding action since the escape of oil from the more restricted vents 36 takes place at a much slower rate. The vents 35 are positioned so that they are covered by the 'p'lunger'32 substantially at the point at which the arc presents the most favorable conditions for interruption by the oil blast. Although the bridging member continues slowly, b reason of the dashpot action, towards its nal open circuit position illustrated in dotted lines, the circuit is generally cleared by the oil blast at the retarded point, the constant length pressure generating arc during this period suppl ing adequate but not excessive pressure. ince the main arc is likewise maintained at a substantially minimum length, the total arcing pressure is therefore minimized. By this arrangement the arc pressure Within the chamber 4 is controlled during separation of the contacts and is directed in the most eflicient manner to interrupt the are within a very short travel of the bridging member;

It will be noted that the plunger 32 like-' wise serves to prevent rebound of the bridging member due 'to the so-c'alled piston effect, since thepressure generated within the chamber 4 exerted on the rod 9 in one direction and on the plunger 32 in the other direction is at least equalized in so far as rebound is concerned, the cross sectional area of the plunger 32 being subject to variation if desired for the purpose of increasing the opening force by the pressure generated within the chamber. 1

It should be understood that my invention is not limited to specific details of construction and arrangement thereof herein illus trated, and that changes and modifications may occur to one skilled in the art without departing from the spirit of my invention.

.What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric circuit breaker of the fluidblast. type comprising a pressure confining casing containing an insulating llqllld, said casing provided with a pressure relief opening, relatively movable contacts forming a pressure generating arc and a second are within said casing, and means maintaining fixed the length of said pressure are during the initial circuit opening movement, the pressure forcing insulating liquid from said casing through said relief opening at high Velocity to interrupt said second arc.

2. An electric circuit breaker comprising a pressure confining chamber containing insulating liquid, said chamber provided with a relief opening freely venting said chamber, relatively movable circuit controlling contacts mounted within said chamber forming two arcs in series, and arcing means limiting to a predetermined and fixed extent the length of one are during the initial circuit opening movement of said contacts, the pressure generated by said fixed are causing a blast of insulating liquid from said chamber across and through the other are which is formed opposite said relief opening.

3. An electric circuit breaker comprising a pressure confining chamber containing an insulating liquid, said chamber vprovided with a pressure relief exhaust opening, coacting circuit controlling contacts within said chamber, said contacts arranged to draw both a pressure generating arc and another are in series therewith adjacent and substantially opposite said relief opening so that arcing pressure generated within said chamber is effective to cause a blast of insulating liquid through said last-named arc and relief opening, and means limiting and maintaining fixed the length of said pressure generating arc during the initial opening movement, thereby preventing generation of excessive pressure within said chamber.

4. An electric circuit breaker comprising a pressure confining casing provided with a relief opening exhausting into a low pressure region, relatively movable contacts separable to form two breaks in series within said chamber including a bridging member and stationary contact structure, one of said breaks formed adjacent and opposite said relief opening, and an arcing member to which the are at the other break is transferred maintaining the arc. length fixed between the same and said bridging member during the initial circuit opening movement of said bridging member, said are generating pressure to cause a blast of insulating liquid from said casing through the arc formed at said relief opening.

5. The combination in an electric circuit breaker comprising a pressure confining chamber containing insulating liquid, said chamber having a pressure relief exhaust opening, and coacting circuit controlling-contacts separable to draw two arcs in series within said chamber, of means limiting to a predetermined and fixed extent the length of one .of said arcs during the initial circuit opening movement, said are generating pressure within said chamber causing a blast of insulating liquid through said second arc and relief opening, and means retarding lengthening of said second arc during said blast.

6. An electric circuit breaker comprising a pressure confining chambercontaining an insulating liquid, said chamber provided with a pressure relief opening, relatively movable circuit controlling contacts" within said chamber, said contacts arranged to draw a pressure generating arc and another are in series therewith adjacent and opposite said relief opening so that a blast of insulating liquid is directed across said last-named arc and through said relief opening to interrupt the circuit, and means retarding said contacts and consequent lengthening of said arcs aftera predetermined initial movement so that excessive pressure in said chamber is precluded and said last-named arc is maintained substantially within said blast of insulating liquid.

7. An electric circuit breaker comprising a pressure confining chamber containing an insulating liquid, said chamber provided with a pressure relief opening, coacting circuit controlling contacts within said chamber including a movable bridging member and stationary contact structure forming two breaksin series, the arc at one of said breaks generating pressure for blasting'insulating liquid from said chamber through saidvrelief opening, the are at the other of said breaks being adjacent and opposite said relief opening and directly in the path of said insulating liquid, and means including dashpot structure operatively connected to said bridging member retarding the opening movement of said bridging member at a predetermined point so that said last-named arc is maintained directly in the path of said blast of insulating liquid during interruption of the circuit.

8l An electric "circuit interrupter comprising a pressure confining chamber containing an insulating ,li'quid, said chamber provided with. a pressure relief opening, coacting circuit controlling contacts including a movable bridging member within said chamber, said contacts arranged to draw a' pressure generating arc and another arc in series therewith opposite said relief opening so that said last-named arc is traversed by a blast of insulating liquid through said relief opening, and dashpot retarding means including a plungerconnected to said bridging i member extending through said chamber for retarding the opening movement of saidbridging member at apredetermined pointopposite said relief opening, .said plunger likewise serving as a pressure equalizer preventing rebound of said bridging member due to pressure generated within said casing.

9. An electric circuit interrupter comprising a pressure confining chamber containing, an insulating liquid, said chamber having a in a predetermined constant length during the initial circuit opening movement, another of said arcs being ad] acent and opposite said relief opening in the path of said blast, and

means retarding said contacts after a predetermined opening movement so that said last-named'arc is wholly within the blast of said insulating liquid during interruption of the circuit.

10. An electric circuit breaker of the fiuidblast type comprising a pressure confining casing containing an insulating liquid, said casing provided with a pressure relief opening, relatively movable contacts forming a pressure generating arc and a second are within said casing, the pressure forcing insulating liquid from said casing through i said relief opening to interrupt said second arc, and means retardingsaid contacts at a predetermined point thereby avoiding generation of excessive pressure within said cas ing during interruption of said second are, said retarding means permittingfurther separation of said contacts at a slower rate.

11. An electric circuit breaker comprising a metallic switch tank containing an insulating liquid, a pressure confining casing within said tank filled with insulating liquid, -circuit controlling contacts mounted within said casing, insulating bushings extending through the top of said tank and within said casing, said bushings connected to said contacts withinsaid casing, a block of insulat ing material forming the upper part of said casing through which said bushings extend, a a metallic plate maintaining said block and bushings in position mounted in said tank,

said insulating material filling said casing between said contacts and metallic plate for providing adequate creepage distance between said contacts and metallic plate and eliminating an air space within said casing.

In witness whereof, I have hereunto set my hand.

WILLIAM E. PAUL. 

